#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>

int main()
{

    int n = 0;
    scanf("%d", &n);
    int sum = 0;
    while (n)
    {
        sum += (n % 10);
        n /= 10;
    }
    printf("%d\n", sum);
    return 0;
}